Steps:

1. Login as kubeadmin
2. Go To Observe > Alerting
3. Switch to Silences tab
4. Create a new silence => It is showing namespace dropdown
5. Expected Result: It should not display namespace dropdown
6. Create this silence
7. Then Edit it => It is showing namespace dropdown
8. Expected Result: It should not display namespace dropdown
9. Expire this silence
10. In this expired silence, click on kebab to Recreate it -> it is showing namespace dropdown
11. Expected Result: It should not display namespace dropdown

Side effect of showing namespace in the Recreate silence and Edit silence:

• if namespace != All Projects changed from Metrics page, for example, when going back to Silences and recreating an expired one, it has label. namespace with empty value. The same for Edit silence, it brings label namespace with empty value.